The opportunity to personalize features in a mobile vehicle is ever increasing as the automobile is being transformed into a communications and entertainment platform as well as a transportation platform. Many new American cars will be installed with some type of telematics unit to provide wireless communication and location-based services. These services may be accessed through interfaces such as voice-recognition computer applications, touch-screen computer displays, computer keyboards, or a series of buttons on the dashboard or console of a vehicle.
Currently, telematics service call centers, in-vehicle compact disk (CD) or digital video display (DVD) media, web portals, and voice-enabled phone portals provide various types of location services, including driving directions, stolen vehicle tracking, traffic information, weather reports, restaurant guides, ski reports, road condition information, accident updates, street routing, landmark guides, and business finders.
For example, traffic and driving directions may be accessed through a voice portal that uses incoming number identification to generate location information based on the area code or prefix of the phone number, or to access location information stored in a user's profile associated with the phone number. Users may be prompted to enter more details through a voice interface.
Speech recognition systems are used within vehicles with telematics units for various functions. The speech recognition unit receives, recognizes and generates responses to commands, such as “Call,” “Dial,” “Locate,” and “Generate map.”
Confidence thresholds are preset in the voice-recognition application software that is installed in the telematics unit. The confidence threshold establishes the minimum acceptable confidence that a spoken word or sentence is correlated with a stored vocabulary in the system. The optimum confidence threshold is set after testing utterances from many people with different dialects under different noise level conditions to obtain statistically significant threshold levels. Different optimum threshold values may be set for different grammar sets to be applicable uniformly across all noise conditions and dialects. The grammar set is associated with a command function and includes all the words that are likely to be uttered during a speech task related to that command function.
Since the optimum threshold values are statistical, they do not meet the needs of everyone in different noise conditions. The threshold values, which are sufficient in low noise conditions, are sometimes inadequate in high noise conditions for a user. The threshold values are sometimes inadequate based on the volume of a particular user. In that case, the speech recognition system is unable, with a confidence greater than the default confidence threshold level, to correlate a spoken phrase with the stored phrases in the speech recognition system. When the user voice command is not recognized because of a low signal-to-noise ratio, the telematics unit advises the user to reduce the ambient noise level. If the user is able to reduce the noise level in the car, for example, by rolling up the vehicle windows, the voice-recognition application may recognize the voice command that is repeated after the noise is reduced. If the voice-recognition application is unable to recognize the command after several attempts, the speech recognition session ends with an unrecognized-command error. The telematics unit advises the user that the voice command was unrecognized. In this case, the user contacts an advisor to provide the desired service.
It is desirable to adjust the confidence threshold level during a speech recognition session, if the signal to noise level prevents the spoken command from being recognized within the default confidence threshold level. It is further desirable to reset to the default confidence threshold level after the vehicle is turned off.